The present invention relates to a semiconductor device and a production method thereof, and specifically to a semiconductor device suitable for use as a solar cell and to a production method thereof.
Hitherto, a semiconductor device has been realized by an inorganic semiconductor such as an element-base semiconductor typified by silicon (Si), etc., a compound semiconductor typified by gallium arsenide (GaAs), etc., and an oxide semiconductor typified by zinc oxide (ZnO), etc. As a typical structure of a semiconductor device, a structure of using an electron or a positive hole as a majority carrier, that is, a so-called pn junction element has been used. Furthermore, a transistor, etc., using many pn junctions have been used for many products as semiconductor devices. An organic material has a merit of realizing by a molecular design the function typified by an organic photoreceptor mounted on a copying machine, a printer, etc., a sensitizer used for photographic films, etc., an organic electro luminescence material, an organic semiconductor, etc. Recently, with regard to an organic semiconductor, research and development of a pn junction, etc., have been carried out as is the case for an inorganic semiconductor, and an effort to the commercialization has been continued.
However, in an inorganic semiconductor, there are problems that in Si, GaAs, etc., in the production of the case of giving a function as a semiconductor device, not only the cost is greatly increased but also a very high technique is required, which is lacking in the simplicity. Furthermore, in a semiconductor device using an inorganic semiconductor only, not only the function of the device is limited by the characteristics of the selected inorganic semiconductor material but also when the device is not prepared in the form of sufficiently taking into consideration of the structural characteristics of the inorganic semiconductor material, such as matching of a lattice constant, etc., whereby causing the deterioration of the characteristics, etc. On the other hand, in the organic material, the cost of the material itself and the production cost of the semiconductor device are relatively low, and also the production of the device is simple. However, it cannot be said that the quality of the organic material is practical in regard to the electrical characteristics such as, mainly, the resistance and the mobility necessary for making function as a semiconductor device. Thus, by combining an inorganic semiconductor and the organic material, the excellent points of both materials in the costs, the simplicity of the production, and the characteristics are utilized, and by giving a specific characteristic to one or both of the inorganic semiconductor and the organic material, the above-described problems can be solved and such a combination can be used as a new element.
The present invention has been made from the above-described viewpoint and provides a semiconductor device excellent in the simplicity of the production and the functional characteristics at a low cost.
As the result of various investigations, the present inventors have found that the above-described problems on the semiconductor device and the production method thereof can be solved by employing a specific material and a specific structure.
This invention provides a semiconductor device, wherein a porous semiconductor layer and an inorganic semiconductor layer are laminated in this order.
The porous semiconductor layer may contains a metal oxide or a compound semiconductor.
The semiconductor device may be used as a solar cell.
An organic substance layer may additionally be formed between a porous semiconductor layer and an inorganic semiconductor.
The organic substance layer may be a monomolecular film of a sensitizing dye.
The porous semiconductor may be titanium oxide or indium copper sulfide.
This invention also provides a method of producing a semiconductor device, wherein a porous semiconductor layer or a semiconductor layer having an organic substance layer on the surface thereof is immersed in a solution containing elements constituting an inorganic semiconductor or compounds containing the constituting elements, and an inorganic semiconductor layer is formed onto the porous semiconductor layer or the organic substance layer in the solution.